The Personal Computer Memory Card International Association (PCMCIA) has defined standards for computer cards which are often referred to as PCMCIA cards and PC cards. PCMCIA cards may provide any of several functions or resources to host devices such as a desktop computer or laptop computer. For example, memory PC cards provide additional memory storage that may be used by a host device. Some PC cards are adapters to one or more defined connector interfaces such as USB, Ethernet, and other IEEE standards. Wireless modem cards facilitate communications between the host device to a wireless network. Wireless signals are transmitted and received through one or more antennas connected to electronics within the modem card. The performance of wireless modem cards conforming to PCMCIA standards is limited, however, due to restrictions on ground connections. PCMCIA standards were originally intended for PC cards that performed functions other than wireless communication. Accordingly, the grounding connection between the host and the modem card through a PCMCIA connector is not intended to provide grounding for radio frequency (RF) circuitry in the modem card. As a result, the ground connection is limited in that it includes relatively thin conductors that introduce inductance and resistance from the host to the ground plane of the modem card. Conventional wireless modem cards utilize unbalanced antennas that require a counterpoise. Since the counterpoise in a conventional PCMCIA wireless modem typically relies on the ground of the device, the PCMCIA connector limits the adequacy of the ground at the wireless modem and, therefore, limits antenna performance. Further, currents on the ground plane caused by radiating energy from the conventional PCMCIA modem card antennas reduce receiver sensitivity.
Therefore, there is a need for a wireless modem card with an antenna having a minimum reliance on the ground provided through the wireless modem connector.